1. Field of the Invention
The present invention relates to a semiconductor light-emitting element and a method for manufacturing the same, and particularly relates to a gallium nitride (GaN) based semiconductor light-emitting element and a method for manufacturing the same.
2. Description of the Related Art
There have been various contrivances for semiconductor layer structures and crystal growth methods in order to increase light-emitting efficiency and performance in semiconductor light-emitting elements such as light-emitting diodes (LEDs) and semiconductor lasers. There have been disclosed, for example, light-emitting elements comprising nitride semiconductor layers in which the p-type impurity concentration gradually decreases (e.g. Patent Reference 1), carrier-overflow prevention layers and impurity diffusion prevention layers (e.g. Patent Reference 2), decreasing crystal defects and suppressing diffusion of impurities into active layers (e.g. Patent Reference 3), improving light extraction efficiency (e.g. Patent Reference 4), and methods for growing semiconductor layers of group III-V nitride compounds having satisfactory crystal quality (e.g. Patent Reference 5).
It is particularly important to improve the efficiency of infusing a carrier into an active layer to increase the light-emitting efficiency of a light-emitting element. For example, the light-emitting intensity of an LED is proportional to the electric current, but when the LED is driven at a high electric current density, the proportional relationship is undone and its light-emitting intensity declines (i.e. a droop phenomenon). For example, Non-patent Reference 1 discloses a study of the droop suppression effect of a p-AlGaN electron blocking layer (EBL) in a GaN-based LED; in particular, a study of forming an area where positive holes collect in the interface between the EBL layer and the p-GaN layer (two-dimensional hole gas-like layer), and suppressing the injection of holes into the active layer at the time of high electric current density.    [Patent Reference 1] JP-A 11-68155    [Patent Reference 2] JP-A 2011-205148    [Patent Reference 3] JP-A 2005-167194    [Patent Reference 4] JP-A 2012-119700    [Patent Reference 5] JP-A 2008-135768    [Non-patent Reference 1] Applied Physics Letters 94, 231123 (2009)